[X86] SimplifyDemandedVectorEltsForTargetNode - add handling for vpmaddwd/vpmaddubsw/vpmulhrsw vector width reduction

[RKSimon]

No description provided.

[llvm-ci]

LLVM Buildbot has detected a new failure on builder ppc64le-mlir-rhel-clang running on ppc64le-mlir-rhel-test while building llvm at step 6 "test-build-check-mlir-build-only-check-mlir".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/129/builds/38591

Here is the relevant piece of the build log for the reference

Step 6 (test-build-check-mlir-build-only-check-mlir) failure: 1200 seconds without output running [b'ninja', b'check-mlir'], attempting to kill
...
PASS: MLIR-Unit :: Interfaces/./MLIRInterfacesTests/11/22 (3846 of 3857)
PASS: MLIR :: Pass/pipeline-parsing.mlir (3847 of 3857)
PASS: MLIR :: IR/parser.mlir (3848 of 3857)
PASS: MLIR :: mlir-tblgen/llvm-intrinsics.td (3849 of 3857)
PASS: MLIR :: mlir-runner/simple.mlir (3850 of 3857)
PASS: MLIR :: mlir-tblgen/op-decl-and-defs.td (3851 of 3857)
PASS: MLIR :: mlir-runner/utils.mlir (3852 of 3857)
PASS: MLIR :: mlir-runner/verify-entry-point.mlir (3853 of 3857)
PASS: MLIR :: mlir-tblgen/cpp-class-comments.td (3854 of 3857)
PASS: MLIR :: Pass/pipeline-options-parsing.mlir (3855 of 3857)
command timed out: 1200 seconds without output running [b'ninja', b'check-mlir'], attempting to kill
process killed by signal 9
program finished with exit code -1
elapsedTime=2538.683663